The present invention relates to an automatic equalizer for canceling rotational unbalance occurring when a rotator is rotated, and relates to a motor incorporating the automatic equalizer.
In various kinds of rotation driving apparatus used for industrial machinery, domestic electric products, or computer, an automatic equalizer is often used to cancel rotational unbalance of a rotator including a rotary shaft.
For example, in the case that the rotator is a disk having bias of weight caused by label of disk face and eccentricity of disk, xe2x80x9ccentrifugal whirlingxe2x80x9d phenomena occurs, which makes a rotary shaft bend largely at certain rotation number. To cancel such the xe2x80x9ccentrifugal whirlingxe2x80x9d, an automatic equalizer keeping rotation balance by inserting plural steel balls into a groove of concentric circles shape was proposed. Such a technique is disclosed in Japanese Patent Publication No. 10-257710A.
There will be explained the related automatic equalizer with reference to FIGS. 1 and 2. A steel ball 45 of balancing member in a case 41 is separated from a magnet 43 with rotation, moves to stable position contacting to an outer circumference wall 41b, and adheres to the magnet 43 at stop of rotation. The related automatic equalizer has a large problem in collision noise with the outer circumference wall 41b and the magnet 43 or running noise (friction noise and rolling noise) caused by movement of the steel ball 45 with such the rotation. Further, there is a problem that the outer circumference wall 41b and the magnet 43 are damage because of impact of collision.
For such the problem, in the publication, there is proposed a method for preventing generation of noise and damage by providing shock absorber made of buffer material such as synthetic resin or rubber at inner face of the outer circumference wall 41b or outer surrounding face of the magnet 43 or by forming similar protect member at surface of the steel ball 45.
However, the method of surface treatment by such the synthetic resin or rubber is rather difficult with high cost.
Further, although aligning action operates corresponding to bias load in vertical face by the steel ball 45 moving to circumference direction, aligning action does not operate to bias load in axial direction. That is, the method does not function as a sufficient automatic equalizer.
It is therefore an object of the invention is to provide an automatic equalizer decreasing collision noise and running noise of a balancer in a case, and realizing a mechanism reducing damage caused by collision with low cost.
Specifically, the object is to provide the automatic equalizer that surface of the balancer is not treated at all by synthetic resin or rubber.
Another object is to provide an automatic equalizer preventing collision noise of each other and damage caused by collision in the unstable condition of the steel ball 45 at low rotation number less than a resonant rotation number CR without using the magnet 43 adhering the steel ball 45 at all.
Further, another object is to provide an automatic equalizer that automatic aligning action operates not only to bias load in vertical face but also to bias load at axial direction.
In order to achieve the above objects, according to the present invention, there is provided an automatic equalizer a motor, comprising:
a cylindrical case provided with a chamber, the case coaxially attached to a rotary shaft of the motor;
a plurality of balancers movably provided within the chamber so as to cancel a rotation eccentricity of the motor; and
a viscous member provided on at least one of surfaces of the balancers and an inner face of the chamber.
In this configuration, collision noise among the balancers and the inner wall of the case can be reduced with low cost. Further, damages due to impact at collision can be prevented with low cost.
Preferably, high viscosity fluid is provided as the viscous member such as silicon oil or magnetic fluid.
Preferably, the high viscosity fluid is coated on at least one of the surfaces of the balancers and the inner wall of the chamber, or injected into the chambers. In this configuration, reducing cost can be realized.
According to the present invention, there is also provided An automatic equalizer a motor, comprising:
a cylindrical case provided with a chamber, the case coaxially attached to a rotary shaft of the motor; and
a plurality of balancers movably provided within the chamber so as to cancel a rotation eccentricity of the motor,
wherein elasticity of at least each surface of the balancers are reduced by annealing.
In this configuration, collision noise among the balancers and the inner wall of the case can be reduced with low cost. Further, damages due to impact at collision can be prevented with low cost.
According to the present invention, there is also provided an automatic equalizer for a motor, comprising:
a cylindrical case provided with a chamber, the case coaxially attached to a rotary shaft of the motor;
a plurality of balancers movably provided within the chamber so as to cancel a rotation eccentricity of the motor;
an inner step portion provided in a center portion of the chamber, for holding the balancers therein when a rotation number of the motor is lower than a predetermined standard rotation number,
wherein the inner step portion has a height which is determined such that the balancer held in the recess portion climbs over the step portion and moves to a region outer than the recess portion by centrifugal force occurring when the rotation number exceeds the standard rotation number.
In this configuration, since the balancers are surely held in the inner step portion, noise and damage due to mutual contact of the balancers can be reduced with simple construction. Further, since the balancers can be moved smoothly, the accurate automatic equalizer and the motor incorporating the same can be realized with low cost.
Since the balancers start to climb over the inner step portion when the rotation number of the motor exceeds the standard rotation number, timing of start to move of each balancer can be managed with high accuracy so as to obtain stable balance performance.
Preferably, the standard rotation number is substantially same as a resonant rotation number of the motor. In this configuration, since the balancers start to move when the rotation number reaches the resonance resonant rotation number which is the earliest timing capable of starting to move, the balancers keep rotation balance extremely quickly.
More preferably, the standard rotation number is higher than the resonant rotation number. In this configuration. the balancers are surely moved to direction keeping balance of the motor.
Preferably, the inner step portion includes a plurality of independent recess portions for holding the respective balancers therein, which are arranged around the rotary shaft with a predetermined pitch. In this configuration, since each balancer in the recess portion is surely held to keep rotation balance at low speed rotation less than the standard rotation number, stable rotation condition is obtained in the entire area of served rotation number.
Preferably, the chamber is provided with:
a holding member formed on an inner face of an outer circumference wall thereof, for holding the balancers thereon when the rotation number of the motor is a rated rotation number which is higher than a resonance rotation number of the motor; and
a slope extending downward from the holding member to the inner step portion to guide the balancers to the inner step portion when the rotation number of the motor becomes lower than the standard rotation number.
In this configuration, each balancer is moved to the inner step portion when the rotation number becomes in low speed rotation state, and stable rotation state is repeated returning each balancer to the inner step portion.
According to the present invention, there is also provided An automatic equalizer for a motor, comprising:
a cylindrical case provided with a chamber, the case coaxially attached to a rotary shaft of the motor; and
a plurality of balancers movably provided within the chamber so as to be movable in an axial direction of the rotary shaft and a circumference direction of the case, for canceling a rotation eccentricity of the motor,
wherein the balancers start to move when a rotation number of the motor exceeds a resonant rotation number of the motor.
In this configuration, the automatic equalizer acts so as to align automatically against not only bias load in the circumference direction of the balancers but bias load in the axial direction.
Preferably, a vertical cross section of an inner face at an outermost portion of the chamber is straight.
Alternatively, a vertical cross section of an inner face at an outermost portion of the chamber is curved. In this configuration, it is possible that each balancer moves smoothly along the inner face of the chamber, so that time till aligning automatically is shortened.
Preferably, a plurality of independent chambers are concentrically provided in the case. In this configuration, the automatic alignment in the circumference direction and the axial direction can be conducted at plural position in the radius direction of the case.
Preferably, the balancers are movable in a radial direction of the case. A dimension of the chamber in the axial direction is made larger toward outside of the radial direction. In this configuration, it is possible to cancel amplification of swing of rotation caused of moving of the balancers at beginning of rotation.